Reinforced acid-pretreatment of Triarrhena lutarioriparia to accelerate its enzymatic hydrolysis Xue Tao a , Juan Li a , Panyue Zhang a,* , Mohammad Nabi a , Shuguang Jin b , Fan Li a , Siqi Wang a , Junpei Ye a a College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China b Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China article info Article history: Received 20 January 2017 Received in revised form 11 March 2017 Accepted 18 April 2017 Available online 14 May 2017 Keywords: Triarrhena lutarioriparia Acid pretreatment Ultrasound Microwave Enzymatic hydrolysis abstract In this study, physical method reinforced chemical pretreatments of Triarrhena lutarior- iparia (TL) were compared to explore the higher reducing sugar yield in subsequent enzy- matic hydrolysis. Four different pretreatments, namely hydrothermal pretreatment (HTP), dilute acid pretreatment (HCl-P), ultrasound assisted acid pretreatment (HCl þ U) and mi- crowave assisted acid pretreatment (HCl þ M) were conducted on TL. The structural fea- tures of TL after different pretreatments were investigated by Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier transformed infrared (FT-IR) techniques. The fractal-like theory was introduced to study the enzymatic hydrolysis ki- netics of TL. Results showed that the reducing sugar yield of HCl-P reached 100.14 mg/g, showing 1.34 times higher than that of the raw. Due to the hemicellulose and lignin removal and lignocellulosic structure destruction, ultrasound and microwave irradiation strengthened the HCl-P, leading to a great enhancement of enzymatic hydrolysis of TL, especially the microwave irradiation. Moreover, the fractal-like theory was confirmed to be satisfactory for studying the enzymatic hydrolysis kinetics of lignocellulosic biomass. © 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Over the past few decades, an increase in excessive and un- sustainable fossil fuel use has led to serious environmental problems, such as large amounts of carbon dioxide emissions and global warming [1]. In order to counteract this serious situation, production of environmental-friendly energy including renewable lignocellulosic biomass has a high pri- ority to ensure global energy security and environmental protection. Fortunately, in more recent years, more attention has been focused on biofuel production from lignocellulosic biomass [2e4]. T. lutarioriparia (TL) is a species of perennial herb with a well-developed rhizome, adapts well to warm and humid environments, and does not compete for land with food with a high biomass productivity more than 22.5 t/(a*ha) [5,6]. This plant has become a notable source of energy plants, and has a great potential for biofuel production. The conversion of lignocellulosic biomass to biofuel is currently a topic of great interest around the world. However, this technology is limited by the poor deconstruction and enzymatic hydrolysis. This resistance is mainly caused by the stable chemical structure and components of raw biomass, * Corresponding author. College of Environmental Science and Engineering, Beijing Forestry University, Qinghua East Road 35, Haidian District, Beijing 100083, China. Fax: þ86 1062336900. E-mail addresses: Taoxuegz@163.com (X. Tao), panyue_zhang@bjfu.edu.cn (P. Zhang). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 42 (2017) 18301 e18308 http://dx.doi.org/10.1016/j.ijhydene.2017.04.149 0360-3199/© 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.